1. Field of the Invention
The present invention generally relates to disk clamp apparatuses, and more particularly, to a disk clamp apparatus to clamp an inner circumference of a record medium having a disk shape which is mounted on a disk mount surface thereof.
2. Description of the Related Art
FIG. 1A is a plan view of a conventional disk clamp apparatus and FIG. 1B is a side sectional view thereof. FIG. 2 is a greatly enlarged detailed vertical sectional view of a disk clamp part of the conventional disk clamp apparatus.
Referring to FIGS. 1A, 1B and 2, the conventional disk clamp apparatus 1 includes a clamper table 4, a clamper top 5, and a clamp member 7, and a core adjusting member 9. The clamper table 4 is rotationally driven by a disk driving motor 3 mounted on a print board 2. The clamper top 5 projects on a center of the clamper table 4. The clamp member 7 is pushed in a radial direction by a spring force of a coil spring 6 provided inside of the clamper top 5. The core adjusting member 9 which is at an outer circumference of the clamper top 5 is clamped at an inner circumference of a record medium having a disk shape (hereinafter “disk”) 8, so that the core of the disk 8 is adjusted to the core of the clamper top 5.
The clamper table 4 is fixed on an upper surface of the disk driving motor 3. An upper surface of the clamper table 4 has a disk mount surface 4a. A friction member 10, having a donut shape and made of a rubber material, is fixed on the disk mount surface 4a. 
Three of the clamp members 7 and three of the core adjusting members 9 are arranged at the clamper top 5 reciprocally. The disk 8 is clamped by the clamp members 7, and thereby the core of the disk 8 is adjusted to the core of the clamper top 5 by the core adjusting members 9.
However, according to the above-described conventional disk clamp apparatus, the core of the disk 8 is adjusted to the core of the clamper top 5 by the respective core adjusting members 9 having intervals of 120 degrees at the clamper top 5 and the disk 8 is clamped by the respective clamp members 7 having intervals of 120 degrees at the clamper top 5. Therefore, since the intervals between of the respective clamp members 7 are relatively wide, a clamp force for clamping a center hole of the disk is generated unevenly. Therefore, it is difficult to keep a surface accuracy of an edge part of a circumference of the center hole of the disk 8.
Hence, when the clamp force having intervals of 120 degrees is applied to the edge part of the circumference of the center hole of the disk, an inner circumference side of a disk record surface is partially deformed. As a result, a problem to reduced record accuracy occurs.
Furthermore, according to the above described conventional disk clamp apparatus, the friction member 10 has an inner diameter (for instance 22 mm) which is larger than an inner diameter of the disk 8 (for instance 15 mm). In addition, a guard part 5a formed together with the clamper top 5 projects on the disk mount surface 4a of the clamper table 4. The guard part 5a faces an innermost circumference part of the disk 8. The guard part 5a has a height lower than a height of the friction member 10.
When the clamp member 7 comes in contact with the inner circumference of the disk 8 caused by a spring force of the coil spring 6, a head end part 7a of the clamp member 7 is pushed against the inner circumference of the disk 8 obliquely-downward with a force F1. Because the inner circumference of the disk 8 is not in contact with the guard part 5a of the clamper top 5, an inner circumference side of the disk 8 is deformed downwardly and an outer circumference side of the disk 8 is pushed upwardly by a force F2, and thereby the record surface of the disk 8 is warped like a cone shape.
According to an actual measurement of a deformation of the disk 8, a position on an outer circumference side of the disk 8 (a position with a radius of 58 mm) is deformed upwardly by 70 μm compared to a position on the inner circumference side of the disk 8 (a position with a radius of 24 mm). Thus, if the record surface of the disk 8 is warped by even a small amount, an error may occur when recording is implemented by irradialting with a laser with an optical pick up.
Particularly, when the disk 8 is clamped in a recording device such as a CD-Re Writable (CD-RW) device to record information, it is necessary to have compatibility with other companies' devices and high accuracy in recording the information. Therefore, if the disk is clamped by the conventional disk clamp apparatus in a state where the inner circumference side of the disk is deformed downward and the outer circumference side of the disk is deformed upward, a problem may occur in that the accuracy of the recorded informetion is reduced.